Polarized snap action magnetic switch



A. E. CHISHOLM POLARIZED SNAP ACTION MAGNETIC SWITCH May 28, 1957 2 Shets-Sheet 1 Filed Dec. 50, 1952 R m M m v w m b m a -H D M H I Z I, b in new E. Fnu M m E a y 1957 A. E. CHISHOLM 2,794,157

POLARIZED SNAP ACTION MAGNETIC SWITCH Filed Dec. 30, 1952 2 Sheets-Sheet 2 INVENTEIR United States Patent PQLARIZED SNAP ACTION MAGNETIC SWITCH Allen E. Chisholm, Portland, Application December 30, 1952, Serial No. 328,715

Claims. (Cl. 317-450) This specification comprises a disclosure of a polarized snap action magnetic switch, hereinafter abbreviated a P. M. switch, together with a disclosure of its use in a novel fire alarm system made possible by the utility of said switch.

The first object of the invention is to provide a snap action magnetic switch having circuit controlling blades which are magnetically biased to either of two circuit controlling positions by permanent magnets, such bias being sufiicient to effectively hold said blades in either of said positions for the purpose of controlling electric circuits, which bias i name the holding bias.

The second object is to provide auxiliary electromagnets which, when momentarily energized by a direct current according to a prearranged plan, will cause said blades to be selectively biased to one of said circuit controlling positions, which bias I name the selective bias.

A third object is to provide selector means whereby the flow direction of the direct current may be selectively reversed in the electro-magnets which reversal will cause one of said magnets to repel one of the permanent magnets, and the other electro-magnet, will concurrently attract the other permanent magnet, thereby to overpower the prevailing holding bias and reverse the circuit controlling blades to contra position, with snap action.

A fourth object is to position the electro-rnagnets in confronting relationship with the permanent magnets so that the repellant-attraction action referred to, supra, will not tend to demagnetize the permanent magnets.

A fifth object is to combine, in a snap action magnetic switch which is responsive to flow direction of a direct current, auxiliary make-and-break circuit controlling means which are responsive to the fiow of said current regardless of the direction of flow.

A summation of the objects, supra, may be said to provide a double throw snap action magnetic switch which may be selectively placed in either circuit controlling position by means of a direct current of momentary application, said current reversible in polarity according to a prearranged plan, whereby the circuit controlling blades will remain in a selected position after said current is interrupted, said position correlated to the flow direction of the current, together with auxiliary circuit controlling means responsive to current make and break whereby a polarity selected circuit may be further controlled by make and break of said current. The controlling direct current may be applied to the electro-magnets momentarily, intermittently or continuously.

Other objects will become apparent to the skilled artizan from the text infra, and are particularly pointed out in the claims.

Drawings, in which similar symbols denote similar parts in the several figures, illustrate embodiments as at present preferred as a means of achieving the stated objects, accompany and form a part hereof, in which:

2,794,157 lc Patented May 28, 1957 Fig. 1 is a plan view of one form of embodiment of the switch;

Fig. 2 is an elevational end view of Fig. 1;

Fig. 3 is an elevational side view of Fig. 1;

Fig. 4 is a partial elevational view of the opposite end of Fig. 1;

Fig. 5 is a partially sectioned view of the magnet carrier 2 and its pivotal mounting components 3 and 4 attached to base 1 of Fig. 1, said view sectioned on plane 5--5 of Fig. 6;

Fig. 6 is an inverted plan view of magnet carrier 2 and its pivot 4, said view sectioned at line 6-6 of Fig. 5;

Fig. 7 is a plan view of a preferred modification of the device shown in Figs. 1 thru 6, which modification will be further described and explained infra;

Fig. 8 is an elevational side view of Fig. 7 in which contact members 24 and 33 are omitted to better illustrate the device;

Fig. 9 is an inverted end view of Fig. 7 which is partially sectioned to illustrate a method of pivotally mounting carrier 2;

Fig. 10 is a circuit diagram illustrating a practical application of my P. M. switch as a component of a fire alarm system in which the electro-rnagnets, switch blades and other parts of said switch are denoted by symbols referring to similar parts of Fig. 7. It will be noted that in Figs. 1 to 7, the permanent magnets, hereinafter specifically described, are illustrated as having tapered polar legs, and that in Figs. 16, the polar legs of the electro-magnets are in closest relationship at their pole face extremities.

The structural details of the invention will now be described.

Referring to Figs. 1 thru 6, a base 1 of insulating material supports the several components of the device. A magnet carrier 2, having a supporting pivot 4, is movably attached to base 1 indirectly by pivot socket 3 which is fastened to said base. A locking device 6, such as a cotter pin, is placed in hole 5 of pivot socket 3 and engages an annular groove in pivot 4-, to retain said pivot in said socket. The pivot may freely rotate in the socket to permit arcuate movement of carrier 2 which has two angular limbs each of which is pierced by two angular slots separated by barriers 2a thru which the legs of permanent magnets 14 and 14:: are placed, the arch of said magnets bearing against said barriers. The magnets are locked in this position by locking straps 13. Said limbs are extended longitudinally to form abutments 2b and 20 which bear alternately against limiting stops 15a and 1512 thereby limiting arcuate movement of carrier 2. Attached to the opposite end of the carrier is an insulating means to which are afiixcd blades 8 and 8a at whose extremes double faced contact buttons 10 and 10a are attached. Contacts 2i, 22, 23, 24, and terminals 25, 26 are suitably positioned and attached to base 1 as a means for conducting electric current to blades 8 and 8a, whereby contacts 21, 22, blade 8 and terminal 25 together with a flexible conductor interconnecting said terminal and said blade, form a double throw switch. Likewise, the other components 23, 24, 3a, and 26 with interconnecting conductor, comprise a similar double throw switch. Both switches operate concurrently by movement of carrier 2, so that when the carrier is positioned as shown in Fig. l, a circuit is established between terminals 25 and contact 22, and another circuit is established between terminal 26 and contact 23, which circuits are switched to their respective opposite contacts 21, 24 when carrier 2 is reversed to contra position. I do not limit the switches, supra, to single pole double throw; each switch may be made multipole double throw by suitable modification in construction.

Dual electro-magnets, each comprising a bobbin, a core therefor, with dual pole pieces attached thereto, and

denoted by the symbols 16 and 16a, are provided with conductor windings 3]. and 32 respectively. Winding 31 connects to terminals 27 and Y28. Winding 32 connects to terminals 29 and 30. Each electro-magnet is'firmly attached to base 1 by clamp bars 13, 19, and clamp screw 20, the pole pieces thereof being positioned between said clamp bars, screw 20 passing thru said bars and threadably engaging base 1. Each of said magnets may thus be adjustably positioned with its pole faces 170 or 17!; in requisite air gap relationship with the oppositely positioned pole faces 12a or 12b of permanent magnets 14 and 14a. Windings 31 and 32 are to be connected, either in series or in parallel, to a source of direct current. Such connections are to be made in a manner so that when excited by the direct current the poles of one electro-magnet will attract its oppositely positioned permanent magnet, and the other electro-magnet will concurrently repel its oppositely positioned permanent magnet. A minimum air gap must prevail between an 'electro-magnet and its opposite permanent magnet when said magnets are in closest proximity, said air gap predetermined by adjustment of limiting stops 15a, 15b in their relationship to abutments 2b, 2c, of carrier 2. Such adjustment also limits the maximum width of the air gap between the other pair of magnets.

When the electro-magnets are deenergized their pole pieces, together with the flux path provided by their bobbin cores, act as magnetic anchors to the magnetic pull from the confronting pole faces of the permanent magnets, and the terms anchor or anchorages will be used hereinafter to define this status of the electro-magnet structures.

Hence, one permanent magnet will be attracted to one anchor with a minimum air gap therebetween, and a maximum air gap will prevail between the other per-manent magnet and its anchor, thereby biasing carrier 2 to one of its limiting stops 15a or 15b. Any force acting to overcome said bias must lengthen the minimum air gap and reduce the existing maximum air gap, thus decreasing the pull of the permanent magnet in closest proximity to an anchorage, and augmenting the pull of the other magnet and its more distant anchorage, the pull of each magnet equal to the square of the gain or loss in air gap of the respective magnets. Thus, a differential between the two air gaps will cause carrier 2 to swing toward the least air gap, and such swing will be augmented in velocity due to the cumulative gain in pull as the air gap diminishes. The permanent magnets will be of sufficient strength so that the carrier will be held firmly against one of its limiting stops, thus insuring adequate pressure between the electrical contacts of the blades.

When the carrier is thus magnetically biased to one limit stop and an actuating force is applied to Widen the lesser air gap until such gap is minutely greater than the V opposite air gap, then the opposite magnet takes over and carrier 2 swings extremely fast to engage its opposite limit stop, whereby blades 8 and 8a make or break a circuit with snap action.

Said actuating force comprises a controlled direct current connected to windings 31 and 32 of the electromagnets which are primarily connected so that when one permanent magnet biases carrier 2 to one of its limit stops, the direction of current flow in said windings creates mutual attraction between the electro-magnet nearest one permanent magnet, and the other electromagnet and its opposite permanent magnet are mutually repellant, under which condition the holding bias of carrier 2 is increased thereby. When the direction of flow of said current is reversed the polarity of both electromagnets is reversed, wherefore the first mentioned magnets repel each other and the second mentioned magnets attract each other, and the magnetic forces thus set up are suflicient to force carrier 2 against its opposite limit stop and reverse blades 8 and 8a to contra position. Obviously, the relative distance of the air gaps is reversed during the transition of carrier 2 from one limit stop to the other limit stop, and the movement of the carrier and its blades is extremely fast.

The text, supra, describes an embodiment of the invention by which achievement of objects 1 thru 4 may be accomplished. Referring to Figs. 7, 8, 9, I will now describe and explain the operation of another embodiment which will achieve all of the stated objects, wherein carrier 2 is modified to an elongated member pivotally supported by pivot 4 which is free to rotate in pivot socket 3 (also modified) attached to base 1. Said pivot is firmly affixed to the median point of carrier 2. Permanent magnets 14 and 14a are attached to carrier 2 by locking straps in a manner similar to that shown in Figs. 1 thru 6. The extremes of members 2, 2b and 20, provide limiting abutments which alternately engage stops 15a and 15b. Blades 3 and 8a are modified as to their form and method of attachment to carrier 2, which modification is clearly illustrated in the drawings thereof. Electro-magnets 16 and 16a are modified in structure and in the means for attachment to base 1. The pole faces 17a and 17!) which confront faces 12:: and 12b of the permanent magnets are bent angularly as shown in Fig. 7, and angular supports 18 are aflixed thereto by welding or other means. Said supports are attached to base 1 by suitable fasteners so that all magnets are equal in elevation above said base, and the electro-magnets are positioned in confronting relationship with the permanent magnets with a minimum air gap between one permanent magnet and a predetermined maximum air gap between the other magnets when an abutment of carrier 2 bears against one of its limiting stops. The polar com ponents of the electro-magnets are extended beyond their bobbin ends to form pole faces 17c and A ferrous armature 37 is hingedly attached to base it by pivot 38 so that it may approach or recede from pole faces 170 of electro-magnet 16. A switch blade 39 is afiixed thereto, said blade having contact buttons and a flexible conductor similar to blades 8 and 8a, so that it can make or break a circuit connected to contacts 33, 36, 46. Said blade is normally held away from pole faces 170 by tension of spring 44 in which position blade 39 bears against contact 33, which limits the maximum air gap between 37 and 17c. When winding 31 is energized, armature 37 is pulled toward pole faces 17c until blade 37 bears against contact 36 thus limiting the minimum air gap between 37 and 170. Electro-magnet Elna is of similar construction to 16, and the description, supra, of 16 is also a description of the components and action of magnet llda, except as to symbols.

In the device described supra, I have provided circuit controlling switch blades which may be selectively moved to control selected circuits by magnetic means responsive to controlled direction of flow of a direct current, and switch blades which may make and/ or break electric circuits in response to make and/or break of said direct current.

The air gaps between magnets are exaggerated in the drawings to better illustrate the details of structure; in actual practice such minimum gap need be only a few thousandths of an inch, and the movement of the magnet carrier, limited by abutments 2b2c and limiting stops lain-15b, may be restricted to ten thousandths of an inch measured at the center line of the magnets, to provide ample make and break at the contact buttons of blades 8 and 8a.

Referring to Fig. 7 it will be noted that when the electro-magnets are not electrically energized the flux path of a permanent magnet may be defined as beginning at the positive pole thereof, thence thru one pole piece of its confronting electro-magnet, thru the bobbin core,-

thence thru the other pole piece to the negative pole of the permanent magnet. The area of the bobbin core will be greater than the polar area of the permanent magnet, hence said flux is short circuited thru said core so that it will not tend to influence the armature of the electro-magnet structure. Fig. is a schematic sketch of a fire alarm system including means for'operation thereof, in which a magnetic switch, similar to that shown in Fig. 7, is advantageously used, wherein sketch S denotes a key type reversing switch including make-and-break elements in groups S3 and S4. This switch is intended to be manually operated by key K, which may remain in neutral position as illustrated or it may be set at any one of positions K1, K2, K3, K4. Said key moves cam C3 to engage blades e-f and blades g-h of group S2 when set at K2 position, thus connecting conductors 48-49 to negative and positive poles respectively of battery B3, or in lieu thereof a rectified source of alternating current. Reversely moving said key to position K3 engages blades 0-01 and blades a-b of group S1 thus reversing the polarity of conductor 48 from negative to positive, and connecting conductor 50 to negative polarity. Conductor 51 connects blades n and j, of groups S3 and S4 respectively, to line conductor 52 which conductor is the control of electro-magnets 16 and 16a of my magnetic switch. Conductor 46 connects blades d-e with positive battery, and conductor 47 connects blades a-h with negative battery. The flow direction of said current determines the circuit selective position of blades 8 and 8a of the magnetic switch, and make and break of said current determines the circuit controlling position of blades 37 and 40.

When key K of switch S is at K1 position the group S2 blades thereof are engaged as noted supra, and blades m-n of group S3 are also engaged which energizes circuit 51-52 to terminal 27 thence thru electro-magnet 16 to terminal 28 thence to 29, thence thru electromagnet 16a to terminal 3%, thence thru conductors 53-48 back to switch S, whereby said magnetic switch is energized to position blades 8 and 8a as illustrated, and attract armatures 37 and 40 to engage blade 39 with terminal 36, and blade 42 with terminal 35. Key K may be moved to position K2 which will deenergize said circuit which will release armatures 37-40, but will not otherwise aifect the position of blades 8 and 8a, which position is predetermined by negative polarity of current at terminal 27.

Thus, when key K is at K1 position, a branch circuit 52-67-26-23 to gong B2 is closed thru blade 8a, and the return circuit therefrom 70-35-45-68-48 is completed by attraction of armature 40, and when key K is at K2 position said circuit is opened indirectly by release of armature 40. Gong B2 is of the single stroke type, and it may sound a coded signal by alternately shifting key K in the Kl-KZ positions.

When key K is moved to position K4 the line current in conductors 48-52 is reversed in polarity at terminals 27-30 of the magnetic switch, which status causes reversal of blades 8 and 8a to contra circuit controlling position, and attacts armatures 37-40, whereby blade 8a energizes circuit 5267-26-8a-24-69, to relay R3 thence thru same to conductors 53-48. Relay R3 then completes an auxiliary circircuit 71-25 thru blade 8, thence thru 21-72 to siren H whose return circuit 74-46-37-36-75 is closed indirectly by attracted armature 37 to activate said siren. Thus by alternately shifting key K from K4 to K3 position, the siren may sound a coded signal by make and break of its circuit by armature 37, or it may sound a continuous blast by retaining key K at position K4. Relay R3 also breaks said circuit but in case of stuck contacts at this relay I deem it best to primarily control the circuit by make-and-break caused by armature 37.

The schematic sketch in Fig. 10 and the description,

supra, discloses controlling means, circuits, and a source of direct current therefor, illustrating one useful application of my magnetic switch. Other circuits, not pertinent to the use of said switch, are shown in said sketch and will now be described to provide a full understanding of the operation of the fire alarm system, said circuits controlling fire detection apparatus.

The detector circuit begins at conductors 59-61 which are connected to another source of current. A gong B1 and pilot lights P1 and P2 are responsive to make and break of blades 65-66 of relays R1 and R2 respectively. D1 and D2 denote thermal responsive circuit breakers which will remain in circuit closing position at normal temperatures, but they will break a circuit at abnormal temperatures such as is caused by a fire. Conductor 61 is connected to conductor 48 whereby 48 becomes a common bus for both the alarm and the detector portions of said system. Relay R1 is continuously energized by detector D1, at normal temperatures, thru circuit 59-57- D1-54-48-61. Relay R2 is similarly energized by detector D2 thru circuit 5'9-58-56-D2-54-48-61. Additional detectors with similar relays and circuits may be added if desired. Relay R1, when energized, closes circuit 59-65-63 to pilot P1 whose return circuit is 62-61-48-61, and when this relay is deenergized by opening of detector D1, pilot P1 is extinguished and circuit 59-65 thru gong B1 to 61-48-61 is closed to activate said gong. Relay R2 functions similar to R1, and will control pilot P2 and activate said gong. Each pilot is assigned a symbol in dot-dash code, which code indicates the geographical location of the detector atfected by a fire. Thus, when a fire open circuits a detector, the location thereof is indicated by black out of its pilot and gong B1 alerts the dispatcher who then alerts the fire fighting crew, and indicates the location of said fire, by manipulation of key K as described supra.

While I have illustrated and described preferred embodiments of my invention and its application to a fire alarm system, it is to be understood that other embodiments, structures, and uses may be made by the skilled artizan without departing from basic scope of the invention.

The overall novelty of this invention lies in positioning two permanent magnets, having bi-lateral pole faces, in movable confronting relationship with two bilateral type electro-magnets, normally deenergized, one of which acts as a magnetic responsive anchorage to the magnetic pull of one of the permanent magnets whereby said magnet is self pulled a limited distance toward said anchorage, and the other permanent magnet is concurrently pulled a limited distance from its confronting electro-magnet structure by the first mentioned permanent magnet thereby indirectly biasing one or more switch blades to a predetermined relationship with connected electric circuits; subsequently when the electro-magnets are excited by a direct current at predetermined polarity, the prevailing magnetic anchorage is nulled and translated into a propellant force in opposition to the pull of its confronting permanent magnet, and the other electro-magnet exerts a cumulative attraction to its confronting permanent magnet which forces combine to pull both permanent magnets a limited distance toward the last mentioned electromagnet; hence, said switch blades are reversed in position and biased to a predetermined contra relationship with said circuits, and when the exciting current is cut off the former magnetic anchorage is nil and the other electro-magnet structure acts as the prevailing magnetic anchorage to maintain that bias of the switch blades.

The placement of both bi-lateral poles of a movable permanent magnet in confronting relationship with both bi-lateral poles of a stationary electro-magnet in mutual bias relationship, as a means of securing maximum flux flow between magnets, is believed to be new and novel in the art of magnetic switches.

It is believed that further novelty exists in combining a polarity responsive magnetic switch, of the character delineated in Fig. 1, with auxiliary switching means re- .sponsive to current flow irrespective of flow direction, comprising the extended bilateral poles 17c and 17c of ,electro-magnets 16 and 16a, and the armatures 37 and 40 with their components as illustrated in Fig. 7.

Having illustrated and described my invention so that the skilled artizan may understand, construct, and use the same, and having pointed out what I believe to be the novelty thereof over present art, what I claim and desire to secure by Letters Patent is:

1. In a polarized magnetic switch adapted to prevent loss of magnetism from its permanent magnet elements, the combination of supporting means, switch contacts mounted thereon including a movable blade responsive to magnetic intiated movement, a swingable magnet carrier associated with said means, a pair of U shaped permanent magnets attached to said carrier in spaced apart relation, the pole faces of one magnet advancing and the pole faces of the other magnet receding in relation to the swing of said carrier, two electromagnet structures aifixed to said supporting means in mutual magnetic relationship to said permanent magnets, each structure comprising a wound bobbin, a core therefor, a pair of bi-lateral pole elements attached to said core the extremes of said elements terminating in a pair of pole faces in co-planar alignment, both pole faces of one structure located in confronting position to the pole faces of one permanent magnet with a minimum air gap therebetween whereby said magnets are, and will remain in conventional charging position when the electromagnet is selectively energized in attractive relation to its permanent magnet, both pole faces of the other structure likewise located in confronting position to the pole faces of the other permanent magnet with a predetermined greater air gap therebetween whereby the greater air gap restricts loss of permanent magnetism from its magnet, due to mutual magnetic repulsion between magnets, to less than the gain in recharging thru the minimum air gap when the magnets are in mutual magnetic attractive relationship, said combination providing means to prevent loss of normal flux value in the permanent magnets substantially as described.

2. A snap action magnetic switch comprising in combination a base, stationary switch contacts attached thereto, switch blades indirectly movable by magnetic forces, a magnet carrier associated with said base and arcuately movable thereon, means to confine the arcuate movement of said carrier within a predetermined limit of extreme movement, means for moving said switch blades by said carrier, two U shaped permanent magnets affixed to said carrier in spaced apart relationship, the polar legs thereof extending transversely with respect to the lon gitudinal axis of said carrier so that both polar faces of one magnet advance and both polar faces of the other magnet recede when rotated in an arcuate path by movement of said carrier, two electromagnet structures attached to said base each structure comprising a wound bobbin, a core therefor, bi-lateral pole pieces attached to said core the faces thereof in co-planar alignment, one of said structures positioned so that both its pole faces confront the pole faces of one of said permanent magnets with a minimum air gap therebetween, the other structure positioned so that its pole faces confront the pole faces of the other permanent magnet in similar magnetic relationship with a predetermined greater air gap therebetween, said air gaps reversible by means of external power to move said carrier, substantially as described.

3. In a snap action magnetic switch as claimed in claim 2 the combination therewith of means to initiate movement of the magnet carrier in said arcuate path, to expand the prevailing minimum air gap and concurrently contract the maximum air gap, to reverse the prevailing air gap relationship between confronting pairs of magnets whereby said carrier reverses its position with snap action substantially as described, said means including a direct current electric circuit to simultaneously energize both electromagnet bobbins at a predetermined maximum current flow value, one bobbin connected in said circuit to produce mutual magnetic attraction between its pole faces and the pole faces of its confronting permanent magnet, the other bobbin connected in said circuit to produce mutual magnetic repulsion between its pole faces and the pole faces of the other permanent magnet. 4. A polarized relay structure operable at maximum magnetic efficiency and comprising in combination, a base including switch contacts mounted thereon, a magnet-carrier pivotally mounted on said base and revolvable in an arcuate path, means to limit the rotation of said carrier in said path to a predetermined maximum, switch blades associated with said carrier and movable therewith to engage said contacts in make-and-break relationship, two U-shaped permanent magnets mounted on said carrier to revolve therewith, said magnets in spaced apart relation the polar limbs thereof transversely positioned with respect to the longitudinal axis of said carrier, both poles of each magnet having polar faces in co-planar alignment, the faces of one magnet rotating clockwise and the faces of the other magnet concurrently rotating counterclockwise With respect to said arcuate path, two electromagnet structures mounted on said base in predetermined confronting relation to said permanent magnets each structure comprising a bobbin, a core therefor, a conductor winding around said core, a pair of bi-lateral pole pieces joined by said core, said pole pieces terminating in a pair of polar faces in co-planar alignment, means for attachment of said structures to said base, one of said structures positioned with its polar faces confronting both polar faces of one permanent magnet in co-active magnetic relationship with a minimum air gap therebetween, said air gap established by restricted rotation of said carrier, the other structure likewise positioned in co-active magnetic relation to the polar faces of the other permanent magnet with a predetermined maximum air gap therebetween, said air gap also established by restricted opposite rotation of said carrier, the magnetic flux emanating from both pole faces of each permanent magnet exerting a pull thru said air gap toward both pole faces of its confronting electromagnet structure to urge said carrier to revolve in the said path, said pull unequal on said carrier and of greater force between the lesser airgap, whereby the placement of said pairs with their polar faces in confronting relation where the flux flow is maximum, effectuates maximum magnetic efiiciency substantially as described.

5. In a magnetic switch to control electric circuits by dual neutral armatures responsive to electro-magnetic influence and by dual polarized armatures responsive to permanent magnetic and/or electro-magnetic forces, the combination of supporting means, switch contacts affixed thereto, dual neutral armatures hingedly supported in spaced apart relation, two electro-magnets fixedly associated with said means in spaced apart relation to each other, each electro-magnet comprising a core, a coil winding on said core, a pair of bi-lateral pole pieces median attached to said core at opposite ends thereof in substantially H-shaped configuration in which the horizontal limb thereof represents said core, the vertical limbs represent said pole pieces, the extremes thereof providing a double pair of polar faces, one of said neutral armatures hingedly positioned in magnetic attractive relation to one pair of said polar faces of one electro-magnet, the other neutral armature positioned in similar magnetic relation to the other electro-magnet, means to urge said armatures away from said polar faces, an elongated magnet carrier, a pivotal support therefor said carrier medianly positioned thereon and removable therearound, two bi-lateral-pole permanent magnets associated with said carrier to revolve therewith in an arcuate path said magnets positioned on said carrier in spaced apart relation from said pivotal support, the poles of one magnet facing the direction of rotation the poles of the other magnet trailing the direction of rotation of said carrier, one of said electro-magnets positioned so that the faces of its other pair of pole pieces confront the pole faces of one of said permanent magnets, the other electro-magnet similarly positioned so that the pole faces of its other pair of pole pieces confront the polar faces of the other permanent magnet including an air gap between each confronting group of said magnets, and switch blades responsive to movement of said armatures and/or said magnet carrier, substantially as described.

References Cited in the file of this patent UNITED STATES PATENTS 344,948 DeSolome July 6, 1886 10 Henry Mar. 28, 1893 Kitsee Dec. 11, 1906 Dodgson Aug. 25, 1908 Allen et al. July 18, 1911 Krum Feb. 22, 1916 Seitz Mar. 26, 1918 Barlow Aug. 10, 1920 Patterson Jan. 2, 1923 Keller Apr. 14, 1931 Lazich Sept. 8, 1931 Larson Apr. 5, 1932 Schweitzer Nov. 17, 1936 FOREIGN PATENTS France Apr. 10, 1933 

